Establishing communication with a called party becomes difficult when that party is mobile. In general, a person wishing to contact a party by telephone initiates a call to a telephone that is in close proximity to that party, such as a home telephone or office telephone. However, the called party may not always be in close proximity to any one particular telephone at all times. Moreover, highly mobile individuals may be located near several different telephones during the course of a day and, thus become difficult to contact without a priori information of their whereabouts. This presents a problem to persons who need to contact a mobile party immediately, regardless of that party's location.
An attempt to solve the problem of establishing communication with a mobile party resulted in the technique known as "Call Forwarding". Call Forwarding is a well-known technique whereby an individual who will be away from her telephone can redirect calls to another telephone. For example, by using Call Forwarding an office worker planning to go on vacation could redirect her calls to an office mate's telephone. Such systems, although desirable, are dramatically limited by their inability to selectively forward calls. Once a subscriber has specified a forwarding number to which the subscriber's calls should be forwarded, all of the subscriber's calls are forwarded to that number, regardless of the time of day, day of the week, identity of the calling party, or status of the telephone to which calls are being forwarded.